Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme最新文献

This study explored the effects of isometric training at long muscle lengths (ISOM) versus full range of motion isotonic training (ISOT) on quadriceps femoris regional hypertrophy. Twenty-three healthy, resistance-trained men and women completed a 6-week, twice-per-week intervention. A within-subject study design was employed with limbs randomized to unilateral ISOM or ISOT knee extension. Muscle thickness was assessed pre- and post-intervention at proximal, middle, and distal sites of the anterior thigh and lateral thigh. Data was analyzed using Bayesian linear mixed-effects models. The between-condition estimate for summed anterior thigh muscle thickness was -0.20 cm (high-density credible intervals (HDI): -0.54, 0.16), with 87% probability of direction (pd), and 75% of the posterior distribution exceeding the region of practical equivalence (ROPE). At the proximal site of the anterior thigh, between-condition estimates showed the greatest directional shift in favor of ISOM (contrast estimate: -0.11 cm (95% HDI: -0.24, 0.02)), with 82% of the posterior distribution exceeding the ROPE. Minimal to negligible changes in summed and regional lateral thigh muscle thickness were found for both conditions. Overall, ISOM and ISOT elicited similar quadriceps hypertrophy in resistance-trained individuals. Isometric training at long muscle lengths may elicit a superior hypertrophic effect in the proximal anterior thigh; however, uncertainty in the effect estimates precludes definitive conclusion in this regard and further investigation is warranted.

Inconsistency among evidence syntheses has led to opposing guidelines and public confusion regarding low- and no-calorie sweeteners (LNCS) in noncommunicable diseases. To understand the role of different analytical approaches in assessing LNCS and cardiometabolic outcomes, we conducted an umbrella review of systematic reviews and meta-analyses. MEDLINE, EMBASE, and Cochrane were searched for systematic reviews and meta-analyses of trials or cohorts that had at least two analytical approaches: naïve (LNCS vs. all-comparators (trials) and prevalent (cohorts)) and bias-adjusted (LNCS vs. intended or reference substitution (trials) and LNCS change or intended or reference substitution (cohorts)). Grading of Recommendations Assessment, Development, and Evaluation assessed certainty of evidence. We included six trial- and five cohort-based analyses. In trials, LNCS reduced energy, body weight, and body fat in both analyses and body mass index and systolic blood pressure in bias-adjusted only, while glycosylated hemoglobin showed smaller reductions than water in bias-adjusted only. In analyses of cohorts, LNCS was associated with higher obesity, diabetes, stroke, and cardiovascular and all-cause mortality in naïve analyses but lower body weight, waist circumference, obesity, coronary heart disease, and cardiovascular and all-cause mortality in bias-adjusted analyses. The certainty of evidence was generally moderate for trials and very low for cohorts. LNCS show benefits across analytical approaches in both analyses of trials. These results agree with bias-adjusted analyses of cohorts, in which LNCS are associated benefits across cardiometabolic outcomes, but not naïve analyses of cohorts. Systematic reviews and meta-analyses using bias-reduction methods support the use of LNCS as a sugar-reduction strategy. Protocol registration: https://doi.org/10.17605/OSF.IO/TSEQM.

The physiological mechanisms involved in augmented cholinergic agonist-induced sweating in exercise-trained individuals remain unclear. This study hypothesizes that nitric oxide synthase (NOS) contributes to augmented pilocarpine-induced sweating in habitually exercise-trained individuals. Endurance-trained and untrained men (n = 15 each) iontophoretically received 1% L-NAME, a NOS inhibitor, and saline (control) in the forearm and then administered 0.001% and 1% pilocarpine to evaluate sweat rate. L-NAME administration attenuated pilocarpine-induced sweating by 10% in the exercise-trained (P = 0.004) but not in untrained (P = 0.764) groups independent of pilocarpine concentrations. Results indicate that NOS partially contributes to increased cholinergic sweating in exercise-trained men.

The modulation of the Hoffmann (H) reflex amplitude during agonist and antagonist muscle contractions provides relevant information on the neural control of leg muscles but remains largely unknown in older adults. This study investigated the H-reflex gain in the soleus muscle at rest and during plantar flexor (PF) and dorsiflexor (DF) muscle contractions performed at 10%, 20%, and 30% of the maximal electromyographic (EMG) activity (EMG_MVC) in 12 young (23-35 years) and 12 old adults (61-76 years). The reflex gain was measured as the slope of the relation between H-reflex amplitude and background EMG activity. The stimulation intensity was set to evoke at rest an H reflex in the ascending phase of its recruitment curve preceded by an M wave (5%-10% of its maximal amplitude; M_max). During PF contractions, the H-reflex amplitude increased with the increase in contraction intensity in both groups with a greater reflex gain (p = 0.024) in young (1.2 (0.5)% M_max/% EMG_MVC) than older adults (0.7 (0.4)% M_max/% EMG_MVC). During DF contractions, the H-reflex amplitude decreased in both groups, with a more negative reflex gain (p = 0.009) in young (-6.8 (2.8)% M_max/% EMG_MVC) than older adults (-2.7 (4.0)% M_max/% EMG_MVC). The decrease in H-reflex amplitude was linearly associated with the increase in tibialis anterior EMG in both groups. The present study showed a smaller reflex gain in older adults in soleus during submaximal PF and DF contractions, suggesting a decreased ability to adjust the excitatory afferent inputs during PF contractions, and to modulate reciprocal inhibition during DF contractions.

Visiting an air-conditioned location during heat exposure reduces physiological strain; however, the effects on gastrointestinal barrier dysfunction and renal ischemia remain unexplored. We compared serum protein responses during a 9 h heat exposure (40.3 °C, 9.3% relative humidity) in 17 older adults without cooling (control) and 19 older adults with a cooling break (∼23 °C) during hours 5 and 6 (cooling). IFABP and sCD14 increased similarly across groups. NGAL was 3.2 pg/mL [1.9, 6.1] lower in the cooling group during heat exposure. A 2 h cooling centre exposure did not ameliorate gastrointestinal barrier dysfunction, but did a reduce a surrogate marker of renal ischemia. ClinicalTrials.gov identifier: NCT04353076.

We aimed to evaluate whether food marketing frequency in recreation and sport facilities (RSFs) in Canada differed by the presence of food sponsorship policies, food sponsorship agreements, and food service contracts. We conducted a cross-sectional study of 85 RSFs using an observational audit using the Food and Beverage Marketing Assessment Tool for Settings (FoodMATS) and a facility survey. All instances of food marketing in RSF were recorded in the FoodMATS and the presence of food sponsorship policies, food sponsorship agreements, and food service contracts from the last fiscal year were reported in the survey by facility managers/directors. Mann-Whitney U tests evaluated differences in food marketing frequency by presence of policies (yes/no), agreements (1+/0), and contracts (1+/0). Food marketing frequency did not differ between RSF with and without a food sponsorship policy (14.5 vs. 18.0, p = 0.37). Food marketing frequency was significantly greater in RSF with food sponsorship agreements (26.5 vs. 12.5, p < 0.001) and food service contracts (60.0 vs. 21.0, p < 0.001), compared to RSF without. Only 22.4% and 16.8% of food marketing instances were linked to current food sponsorship agreements and food service contracts, respectively. Sponsorship agreements and contracts may contribute to food marketing in RSF, but they do not explain all marketing instances. Future research should seek to clarify the origin of food marketing exposures, and the opportunities to use policy documents (e.g., facility policies, sponsorship agreements, and food service contracts) to improve healthy food environments, including food marketing in RSF.

Early detection of hyperinsulinemia may help identify and prevent metabolic diseases, but accurate insulin measurement is challenging, costly, and requires blood samples. This study aimed to characterize saliva insulin responses to a standardized meal tolerance test in people with different body mass index (BMI) classes to help develop potential saliva insulin thresholds based on varying levels of insulin resistance. A total of 94 healthy normoglycemic adults (aged 18-69 years, fasting blood glucose 5.2 ± 0.5 mmol/L) were recruited, categorized into groups with normal weight (NW, n = 41), overweight (OW, n = 23), and obesity (OB, n = 30). Participants fasted for ≥4 h and then consumed a standardized liquid meal (350 kcal; 45 g carbohydrate, 20 g protein, 11 g fat). Saliva samples and finger prick blood glucose were collected at fasting, 60 min, and 90 min post-meal. Saliva insulin levels at all time points were significantly higher in the group with OB compared to OW (all P ≤ 0.02) and NW (all P ≤ 0.001). The OW group also had higher insulin levels compared to NW (all P ≤ 0.02). No significant differences in fasting and post-meal glucose levels were found among groups (all P ≥ 0.12). Strong positive correlations were observed between obesity markers (waist circumference, BMI) and saliva insulin levels. Preliminary cut-off values for fasting (∼16 pmol/L), 60 min (∼97 pmol/L), and 90 min (∼115 pmol/L) saliva insulin may delineate between normal and hyperinsulinemic responses. Saliva insulin can effectively differentiate hyperinsulinemic responses among normoglycemic individuals with varying body weights and waist circumference, suggesting its potential as a non-invasive screening tool for metabolic disease risk.

Endurance exercise significantly enhances energy expenditure with lipids serving as a crucial energy source for skeletal muscle during exercise. The adipocytokine zinc-α2-glycoprotein (ZAG) in endurance exercise remains largely uncertain. This study utilized ZAG knockout and overexpression mice to investigate ZAG's role in regulating lipid metabolism in skeletal muscle during endurance exercise. Results showed the serum ZAG level of mice was significantly increased after exercise, and ZAG knockout mice decreased the exercise performance. Subsequent research revealed that ZAG knockout notably elevated triglyceride (TG) level in skeletal muscle and reduced the expression of lipolysis-related factors such as adipose triglyceride lipase (ATGL), carnitine palmitoyl transferase-1b (CPT1b), and acyl-CoA synthetase long chain family member 1, while enhancing the expression of lipid synthesis factor fatty acid synthase during exercise. The expressions of mitochondrial energy metabolism related factors uncoupling protein 2 and cytochrome c oxidase subunit I were reduced in ZAG knockout mice during endurance exercise. To assess ZAG's impact on lipid metabolism in skeletal muscle, we used ZAG overexpression plasmid in mice and C2C12 cells. ZAG overexpression decreased TG levels, enhanced ATGL expression, and increased CPT1b expression. In conclusion, ZAG can improve the level of skeletal muscle lipid metabolism and mitochondrial function during exercise, and improve the endurance exercise performance of mice.

Prolonged sitting reduces lower-limb resistance vessel function (RVF), whereas increasing aerobic fitness levels enhance lower-limb RVF. However, it is unknown whether having higher aerobic fitness offers protection against prolonged sitting-induced declines in RVF. This study investigated the relationships between aerobic fitness versus reductions in lower-limb RVF following a 3 h bout of uninterrupted sitting. In 30 healthy young adults (19♀, 24 ± 6 years), aerobic fitness was assessed during a graded, maximal cycling test. Relative peak oxygen consumption (V̇O₂peak) was determined via indirect calorimetry (37.5 ± 8.6 (24.7-60.7 mLO₂/kg/min). Popliteal blood flow (PBF) was recorded via duplex ultrasonography. Lower-limb RVF was assessed in the seated posture and quantified as the peak PBF and area under the curve (PBF_AUC, first minute of hyperemia) responses to 5 min of distal cuff-induced ischemia. The lower-limb RVF assessment was performed before and after a sitting. Peak PBF decreased following sitting (473 ± 254 to 387 ± 199 mL/min, P = 0.024), while PBF_AUC remained unchanged (6145 ± 3063 versus 6446 ± 3826 mL, P = 0.758). Relative V̇O₂peak was not associated with Pre-sitting peak PBF (R = 0.236, P = 0.210) or PBF_AUC (R = -0.026, P = 0.889). Furthermore, relative V̇O₂peak was also not associated with sitting-induced reductions in peak PBF (R = -0.145, P = 0.444). The reductions in peak PBF following sitting support previous work demonstrating that prolonged uninterrupted sitting negatively impacts lower-limb RVF. In contrast, prolonged sitting did not alter the PBF_AUC response, suggesting that peak PBF responses may provide a more sensitive index of sitting-induced declines in RVF. In young, healthy individuals, aerobic fitness did not impact baseline or sitting-induced reductions in lower-limb RVF.